The biggest star in boxing is set to take on the biggest star in mixed martial arts.

FOX's Matt Napolitano reports:

That's audio from an Instagram post by undefeated champion boxer Floyd Mayweather Jr. confirming he will duke it out with UFC champion Conor McGregor in a boxing match on August 26 at the MGM Grand in Las Vegas.

McGregor taking to Twitter a short while after to confirm that the fight is officially on.

The announcement coming Wednesday hours after Mayweather Promotions was given permission by the Nevada State Athletic Commission to advertise the fight.

The Mayweather-McGregor bout has been a constant back and forth over finances of the fight as well as trash talking between two of the most outspoken fighters out there.

The fight will air August 26 on Showtime pay-per-view.

Matt Napolitano, FOX News.

Follow Matt Napolitano on Twitter: @MattNapolitano